What will happen if I inject Vitamin B6,B12 - get the oil from the capsule with a needle- into a blood vain in my arm? Will I die or will it help with better absorpsion.

Technically, there are vitamin B injections available in clinics and hospitals, HOWEVER, those are solutions made specifically for injections. You can't just break open a capsule that is meant for ingestion and then inject it into your arm. Vitamin B in gel capsules have relatively high viscosity, and will probably cause a bad reaction in your blood vessels. Granted, this is assuming that you are actually trained in finding a vein and sticking yourself with a needle.

I don't recommend doing this.

Perhaps if you told us what you're trying to achieve, we can offer you a better solution.

First if you had a vial of injectable B12 You would not inject it into your vein. You can have B12 perscribed to you from your doctor. It should be perscribed IM( in the muscle). B12 is one of the vitames that is relatively safe as far accumating too much in your system but the usual perscribed dosage is 1000mg usually once a month but can be taken every two weeks if perscribed that way. No way would you inject B12 Intravein. What would be the purpose?